"I've only changed jobs once, so it's not a decision to be taken lightly," says Rick Leaman, who left UBS to join former colleague Ken Moelis at his boutique investment bank, Moelis & Co. LLC, on July 6. "Kenny presented an opportunity to me that was entrepreneurial, new, and it fit me," Leaman says. "It was the right time in my career to make a change, so I did it."

Leaman, 47, had spent the bulk of his 24-year career at UBS and its predecessor, Dillon, Read & Co. "I've been at my prior firm or entities they acquired for 18 years," he says. "It's a long time to do one thing." Along the way, he worked on some of the firm's most high-profile deals, including advising Vodafone Group plc, a joint partner with Verizon Communications Inc., in a $28.1 billion buyout of Alltel Corp. in 2008, and International Paper Co. in its $6 billion acquisition of Weyerhaeuser Co.'s packaging business that same year.

Leaman joined Dillon Read from Smith Barney in 1992 and became head of M&A in 1997, one year before the firm's parent, Swiss Bank Corp., merged with UBS. In 2004, Moelis, who had joined UBS from Credit Suisse First Boston three years earlier to lead its expansion into U.S. investment banking, promoted Leaman to global co-head of M&A and, in 2005, to global co-head of investment banking. When Moelis left to start his own shop in 2007, Leaman, along with Alex Wilmot-Sitwell, took over Moelis' responsibilities as president of the investment bank.

Steering the investment bank "was a very exciting path at that time," says Leaman, explaining why he didn't initially follow Moelis to his new firm. "It presented a lot of opportunities, and I wanted to pursue those."

At Moelis, Leaman will be a managing director and sit on the management committee, the bank's leadership group. He counts recruiting and mentoring younger bankers as part of his responsibilities, but he will largely concentrate on bringing in clients to the firm.

For UBS, Leaman's departure is hardly a surprise. He was named chairman of the investment banking unit in 2009, primarily a client-facing role, leaving administrative responsibilities to Jimmy Neissa and John Wall. One senior banker at the firm says it had long been a question of when and not if Leaman left, especially in light of UBS' troubles, which include allegations by the U.S. Internal Revenue Service of aiding tax fraud, as well as several high-profile departures. These included the defection of UBS' entire healthcare group, led by Benjamin Lorello, to Jefferies & Co. last year. The senior banker notes that UBS management has been reluctant to pay out bonuses to bankers, which made leading the investment banking group particularly difficult.